The present invention relates to a chuck for axially clamping a tool to a machine tool spindle. The tool has a hollow, sleeve-like shank introducible in the direction of the central axis into an axial bore of a frontal terminus of the machine tool spindle. The tool is tightened in the axial direction by means of spreading members which are uniformly distributed around the central axis and are spread apart by means of a central clamping drive and thus exert a force on the interior wall of the tool shank. As a result, a rearward annular radial face of the tool is pulled into an approximately planar contact with an opposing frontal face of the end of the machine tool spindle. Such a chuck is disclosed, for example, in published European Application 310,942, to which corresponds U.S. Pat. No. 4,863,323 or German Patent document 3,007,440, to which corresponds U.S. Pat. No. 4,406,195.
The spindles of up-to-date machine tools operate at very high circumferential velocities and, due to their high cutting power, are subject to intensive heating. For this reason, generally chucks are used where the tools are pulled into a face-to-face contact against a planar counter-surface of the machine spindle so as to ensure high axial precision and rigidity. The clamping takes place from the inside outwardly with respect to the tool shank to thus reliably absorb the centrifugal forces which are unavoidable at the high circumferential velocities.
Reliable clamping requires very high clamping pressures. It is disadvantageous if these pressures are absorbed as point-type loads by the members of the clamping drive.